The Navy's 844-foot-long amphibious assault ship Essex has slipped into dry dock at General Dynamics NASSCO for at least $150 million in repairs and upgrades, one of the biggest jobs of its kind ever undertaken at the San Diego shipyard.

The maneuver was completed early Monday when the Essex was guided into a floating dry dock, which was then drained of water to reveal the ship's massive steel hull. The "Iron Gator" -- which carries Harrier jump jets and helicopters -- had not been fully out of the water for 12 years, according to the Navy.

Essex, which displaces more than 40,000 tons when loaded for combat, is the biggest Navy ship that can fit into dry dock at NASSCO, the last major shipbuilder on the West Coast.

The money for the ship's overhaul was appropriated before sequestration kicked in, so the work is expected to go forth without interruption. The Essex project involves hundreds of employees from NASSCO as well as BAE Systems and Continental Maritime. Those shipyards often collaborate on major undertakings.

Navy officials said maintenance on eight other ships is likely to be deferred because of federal budget cuts mandated by sequestration.

The Essex was most recently deployed to Japan. It was brought to San Diego for an overhaul after similar work was performed on a sister ship, the Bonhomme Richard. The Navy later conducted a hull swap: The crew of the "Bonnie" sailed Essex to San Diego, while the crew of Essex took over operation of the Bonhomme Richard, which is now stationed in Japan. Such swaps are common in the Navy these days.